Image reader detecting leading or trailing end document sheet in response to change in light receiving state

ABSTRACT

An image reader is provided, which includes a light guide unit forming an optical path to guide light emitted by a first light emitting portion of a first reading unit to a second light receiving portion of a second reading unit, which optical path passes across a feeding path in a detection position such that a document sheet passing through the detection position on the feeding path blocks the light on the optical path, and a controller determining that a leading end or a trailing end of the document sheet passes through the detection position in response to detecting a change in a light receiving state of the second light receiving portion when the document sheet passes through the detection position with the first light emitting portion emitting light and a second light emitting portion of the second reading unit not emitting light.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119 from JapanesePatent Application No. 2010-042578 filed on Feb. 26, 2010. The entiresubject matter of the application is incorporated herein by reference.

BACKGROUND

1. Technical Field

The following description relates to one or more image readers.

2. Related Art

So far, an image reader has been proposed, which is configured to readimages on both sides of a document sheet with two image sensors. In theimage reader, after a document detecting sensor detects a leading end ofthe document sheet, each of the two image sensors separately begins tocapture image data of a corresponding one of the sides of the documentsheet after a lapse of a predetermined time for the corresponding one ofthe sides. Further, after the document detecting sensor detects atrailing end of the document sheet, each the two image sensorsseparately stops capturing the image data at a time when a predeterminedtime for the corresponding one of the sides has elapsed.

SUMMARY

However, the known image reader needs to have the document detectingsensor to detect the leading end and/or the trailing end of the documentsheet, separately from the two image sensors. Thus, it leads to increasein a manufacturing cost of the image reader.

Aspects of the present invention are advantageous to provide one or moreimproved techniques for an image reader, which techniques make itpossible to detect a leading end and a trailing end of a document sheetwithout any special sensor provided separately from image sensors.

According to aspects of the present invention, an image reader isprovided, which includes a first reading unit that includes a firstlight emitting portion configured to emit light onto a first side of adocument sheet, and a first light receiving portion configured toreceive the light reflected from the first side of the document sheet,so as to read out an image having a plurality of pixels arranged along amain scanning direction from the first side of the document sheet, asecond reading unit that includes a second light emitting portionconfigured to emit light onto a second side opposite to the first sideof the document sheet, and a second light receiving portion configuredto receive the light reflected from the second side of the documentsheet, so as to read out an image having a plurality of pixels arrangedalong the main scanning direction from the second side of the documentsheet, a feeder configured to feed the document sheet along a feedingpath in a sub scanning direction perpendicular to the main scanningdirection, a light guide unit that forms an optical path to guide thelight emitted by the first light emitting portion to the second lightreceiving portion, which optical path passes across the feeding path ina detection position such that the document sheet passing through thedetection position on the feeding path blocks the light that is guidedon the optical path from the first light emitting portion to the secondlight receiving portion, and a controller configured to determine thatone of a leading end and a trailing end of the document sheet passesthrough the detection position, in response to detecting a change in alight receiving state of the second light receiving portion when thedocument sheet passes through the detection position in a state wherethe first light emitting portion is set ON to emit the light and thesecond light emitting portion is set OFF not to emit the light.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG. 1A is a perspective view of a multi-function peripheral (MFP)having an image reader in a state where a flatbed cover is closed in anembodiment according to one or more aspects of the present invention.

FIG. 1B is a perspective view of the MFP in a state where the flatbedcover is open in the embodiment according to one or more aspects of thepresent invention.

FIG. 2 is a cross-sectional side view showing an internal configurationof a scanning unit in the embodiment according to one or more aspects ofthe present invention.

FIG. 3 is a cross-sectional side view showing a section A indicated inFIG. 2 in an enlarged manner in the embodiment according to one or moreaspects of the present invention.

FIGS. 4A to 4D schematically show positional relationship between adocument sheet being conveyed and an optical path extending from a lightguide to a second image sensor, respectively, in a state before aleading end of the document sheet reaches a detection position (see FIG.4A), a state just after the leading end of the document sheet hasreached the detection position (see FIG. 4B), a state just after theleading end (or a reading start point) of the document sheet has reacheda reading position for the second image sensor (see FIG. 4C), and astate just after a trailing end of the document sheet has passed throughthe detection position (see FIG. 4D) in the embodiment according to oneor more aspects of the present invention.

FIG. 5A is an illustration to show a positional relationship among afirst image sensor, the second image sensor, and the light guide whenviewed from a right side in the embodiment according to one or moreaspects of the present invention.

FIG. 5B is a graph showing a light receiving state of the second imagesensor which receives light from the light guide in the embodimentaccording to one or more aspects of the present invention.

FIG. 5C is a graph showing a light receiving state of the second imagesensor which cannot receive light from the light guide in the embodimentaccording to one or more aspects of the present invention.

FIG. 6 is a block diagram showing a control system of the MFP in theembodiment according to one or more aspects of the present invention.

FIG. 7 is a flowchart showing a procedure of a process to be executed bythe MFP in the embodiment according to one or more aspects of thepresent invention.

FIG. 8A is a flowchart showing a procedure of a process to feed a firstdocument sheet and detect a leading end thereof in the embodimentaccording to one or more aspects of the present invention.

FIG. 8B is a flowchart showing a procedure of a process to acquire imagedata of a second side of an n-th document sheet in the embodimentaccording to one or more aspects of the present invention.

FIG. 9A is a flowchart showing a procedure of a process to acquire imagedata of both sides of the n-th document sheet and detect a trailing endthereof in the embodiment according to one or more aspects of thepresent invention.

FIG. 9B is a flowchart showing a procedure of a process to feed the n-thdocument sheet, detect a leading end thereof, and acquire image data ofa first side of an (n−1)-th document sheet in the embodiment accordingto one or more aspects of the present invention.

FIG. 10A is a flowchart showing a procedure of a process to acquireimage data of the second side of the n-th document sheet and acquireimage data of the first side of the (n−1)-th document sheet in theembodiment according to one or more aspects of the present invention.

FIG. 10B is a flowchart showing a procedure of a process to acquireimage data of the first side of the n-th document sheet in theembodiment according to one or more aspects of the present invention.

FIG. 11A is a table showing a first control pattern in the embodimentaccording to one or more aspects of the present invention.

FIG. 11B is a table showing a second control pattern in the embodimentaccording to one or more aspects of the present invention.

DETAILED DESCRIPTION

It is noted that various connections are set forth between elements inthe following description. It is noted that these connections in generaland, unless specified otherwise, may be direct or indirect and that thisspecification is not intended to be limiting in this respect. Aspects ofthe invention may be implemented in computer software as programsstorable on computer-readable media including but not limited to RAMs,ROMs, flash memories, EEPROMs, CD-media, DVD-media, temporary storage,hard disk drives, floppy drives, permanent storage, and the like.

Hereinafter, an embodiment according to aspects of the present inventionwill be described with reference to the accompanying drawings.

[Configuration of MFP]

A multi-function peripheral (MFP) 1 shown in FIGS. 1A and 1B hasmultiple functions such as a printing function, a copy function, and afacsimile function, as well as a scanning function required for the MFP1 to serve as an image reader. In the following description, anup-to-down direction, a left-to-right direction, and a front-to-reardirection will be defined based on the directions shown in the relevantdrawings, for the sake of easy understanding of relative positionalrelationship among elements of the MFP 1.

The MFP 1 includes a main unit 2 and a scanning unit 3 provided abovethe main unit 2. The scanning unit 3 is configured to be open and closedrelative to the main unit 2 in response to a front end of the scanningunit 3 being turned up and down around a rear end thereof. When settingthe scanning unit 3 into an open state (not shown) from a closed stateshown in FIG. 1A by using the aforementioned open/closed mechanism ofthe scanning unit 3, a user can conduct maintenance on an internalmechanism incorporated in the main unit 2.

The scanning unit 3 includes a document table 3A configured such that adocument sheet is placed thereon, and a cover 3B configured to cover anupper side of the document table 3A. The cover 3B is configured to beopen and closed relative to the document table 3A when a front endthereof is turned up and down around a rear end thereof. When settingthe cover 3B into an open state shown in FIG. 1B from a closed stateshown in FIG. 1A by using the aforementioned open/closed mechanism ofthe cover 3B, the user can place the document sheet on the documenttable 3A.

Further, the cover 3B is configured to be displaced relative to thedocument table 3A in the vertical direction. This displacement mechanismis provided to the cover 3B, separately from the aforementionedopen/closed mechanism. Thereby, even though a relatively thick documentsheet is to be placed on the document table 3A, the document sheet canbe set on the document table 3A in a state sandwiched between thedocument table 3A and the document cover 3B.

[Detailed Configuration of Scanning Unit]

A detailed explanation will be provided about the scanning unit 3 withreference to FIG. 2. The scanning unit 3 is configured with an automaticdocument feeder (ADF) 5 added to a flatbed (FB) scanner. Further, thescanning unit 3 includes a first image sensor 11 and a second imagesensor 12. In the embodiment, each of the first and second image sensors11 and 12 employs a contact image sensor.

The first image sensor 11 is mounted on a carriage 15 provided in thedocument table 3A and configured to move in the left-to-right directiontogether with the carriage 15. Further, there is an FB glass 17 providedabove the moving path of the first image sensor 11.

When the scanning unit 3 is used as an FB scanner, the document sheet isplaced on the FB glass 17. In this case, the first image sensor 11 readsan image on the document sheet by repeatedly capturing image data of aplurality of pixels aligned along a main scanning direction while movingin a sub scanning direction. It is noted that the main scanningdirection is defined as the front-to-rear direction of the MFP 1, andthe sub scanning direction is defined as the left-to-right direction ofthe MFP 1.

Additionally, in the scanning unit 3, a first ADF glass 21 is disposedin a position that is above the moving path of the first image sensor 11and on a left side relative to the FB glass 17. A second ADF glass 22 isdisposed above the second image sensor 12. A first pressing member 23 isdisposed above the first ADF glass 21. A second pressing member 24 isdisposed above the second ADF glass 22.

When the scanning unit 3 is used as an ADF scanner, the first imagesensor 11 moves to a position beneath the first pressing member 23 inthe left-to-right direction, and stops in the position. The second imagesensor 12 is disposed in a position beneath the second pressing member24 in the left-to-right direction, and fixed in the position so as notto move therefrom in the left-to-right direction.

The document sheet, fed by the ADF 5, is conveyed along a feeding pathindicated by a dashed line in FIG. 2 and passes through between thesecond ADF glass 22 and the second pressing member 24. At that time, thesecond image sensor 12 reads an image on a second side (a down-facingside at the time when the document sheet passes over the second imagesensor 12) of the document sheet, by repeatedly capturing image data ofa plurality of pixels aligned in the main scanning direction (i.e., thefront-to-rear direction of the MFP 1) from the document sheet that ismoving in the sub scanning direction (i.e., a feeding direction).

The document sheet, fed by the ADF 5, passes through between the firstADF glass 21 and the first pressing member 23 after passing throughbetween the second ADF glass 22 and the second pressing member 24. Atthat time, the first image sensor 11 reads an image on a first side (adown-facing side at the time when the document sheet passes over thefirst image sensor 11) of the document sheet, by repeatedly capturingimage data of the plurality of pixels aligned in the main scanningdirection (i.e., the front-to-rear direction of the MFP 1) from thedocument sheet that is moving in the sub scanning direction (i.e., thefeeding direction).

Namely, to read the images from both the first and second sides of thedocument sheet, the second image sensor 12 is controlled to start imagereading earlier than the first image sensor 11. Thereafter, at the timewhen the document sheet reaches a position to face the first imagesensor 11, the first image sensor 11 is controlled to start imagereading. It is noted that the user can arbitrarily configure a settingto make a choice between double-side reading with both the first andsecond image sensors 11 and 12 and single-side reading with one of thefirst and second image sensors 11 and 12.

[Detection of Leading and Trailing Ends of Document]

Subsequently, an explanation will be provided about a configuration todetect the leading end and the trailing end of the document sheet, withreference to FIGS. 3 to 5.

In the scanning unit 3, a light guide 27 is disposed in an areaextending from an upper side of the first ADF glass 21 to a lower sideof the second ADF glass 22. As shown in an enlarged manner in FIG. 3,the light guide 27 is configured to guide light emitted by a lightemitting portion 11 a of the first image sensor 11 to a light receivingportion 12 b of the second image sensor 12.

Specifically, the first image sensor 11 is configured to emit, from thelight emitting portion 11 a, light to be incident onto the documentsheet and receive light reflected from the document sheet with a lightreceiving portion 11 b. Further, the second image sensor 12 isconfigured to emit, from a light emitting portion 12 a, light to beincident onto the document sheet and receive light reflected from thedocument sheet with the light receiving portion 12 b.

Further, when the image sensor 11 reads out the image from the documentsheet being fed by the ADF 5, the image sensor 11 moves to an ADFreading position as shown in FIG. 3 along the sub scanning direction(the left-to-right direction in FIG. 3). The light guide 27 is disposedin a position where when the image sensor 11 emits light from the lightemitting portion 11 a in the ADF reading position, the emitted light isincident onto a lower end of the light guide 27.

The light, emitted by the light emitting portion 11 a of the first imagesensor 11 located in the ADF reading position, is transmitted throughthe light guide 27 and reaches an upper end of the light guide 27, asindicated by an outline arrow in FIG. 3. Then, the light is emitted fromthe upper end of the light guide 27 toward a reflection surface 24 athat is disposed at a right side of the second pressing member 24.Thereafter, the light, reflected from the reflection surface 24 a, isreceived by the light receiving portion 12 b of the second image sensor12.

In this state, when conveyed by the ADF 5, a document sheet D passesthrough between the second ADF glass 22 and the second pressing member24, as illustrated in FIGS. 4A to 4D. At the time when the leading endof the document sheet D is in a position upstream relative to the upperend of the light guide 27 on the feeding path (see FIG. 4A), an opticalpath extending from the light guide 27 to the light receiving portion 12b is not blocked by the document sheet D.

Meanwhile, when the leading end of the document sheet D passes through aposition (a detection position) on the optical path extending from thelight guide 27 to the light receiving portion 12 b (see FIG. 4B), theoptical path is blocked by the document sheet D such that the lightemitted from the light guide 27 does not reach the light receivingportion 12 b.

After that, when the document sheet D is fed by a predetermined distance(see FIG. 4C), the leading end (or a reading start point) of thedocument sheet D reaches a reading position just above the second imagesensor 12. Accordingly, at and after the above time, the second imagesensor 12 can read out the image from the document sheet D, as the lightemitted by the light emitting portion 12 a is reflected from thedocument sheet D and received by the light receiving portion 12 b.

After that, when the document sheet D is further conveyed, the trailingend of the document sheet finally passes through the position (thedetection position) on the optical path extending from the light guide27 to the light receiving portion 12 b. Consequently, in such a state,the optical path extending from the light guide 27 to the lightreceiving portion 12 b is not blocked by the document sheet D.

Accordingly, based on a change in the light receiving state of the lightreceiving portion 12 b as described above, it is possible to detectwhether the leading/trailing end of the document sheet D passes throughthe position (the detection position) on the optical path extending fromthe light guide 27 to the light receiving portion 12 b. A specificexplanation will be provided later about control for detecting theleading/trailing end of the document sheet D.

As depicted in FIG. 5A, the lower end of the light guide 27 faces thefirst image sensor 11 in a position outside a width of the firstpressing member 23 in the front-to-rear direction (at a front siderelative to the first pressing member 23 in the front-to-reardirection). Therefore, even though a document sheet is conveyed betweenthe first ADF glass 21 and the first pressing member 23, the lightemitted by the light emitting portion 11 a is incident onto the lowerend of the light guide 27.

Meanwhile, the upper end of the light guide 27 faces the second pressingmember 24 (the reflection surface 24 a) in a narrow range located in acenter in a width direction (the front-to-rear direction in FIG. 5A) ofthe second pressing member 24. Therefore, when the light receivingportion 12 b performs scanning in the main scanning direction in a statewhere the light emitting portion 11 a emits light and the light emittingportion 12 a does not emit light, the light receiving portion 12 b canreceive the light only in a partial range around the center thereof inthe main scanning direction.

Nonetheless, the light receiving portion 12 b can receive the light onlywhen there is not a document sheet between the second ADF glass 22 andthe second pressing member 24. When there is a document sheet betweenthe second ADF glass 22 and the second pressing member 24, the opticalpath, extending from the upper end of the light guide 27 to the lightreceiving portion 12 b via the reflection surface 24 a, is blocked bythe document sheet.

Hence, when there is not a document sheet between the second ADF glass22 and the second pressing member 24, the second image sensor 12 outputsan image signal having a peak around a center as shown in FIG. 5B.Meanwhile, when there is a document sheet between the second ADF glass22 and the second pressing member 24, the second image sensor 12 outputsan image signal with no peak around a center as shown in FIG. 5C.

In other words, when the document sheet D is conveyed from a position asshown in FIG. 4A to a position as shown in FIG. 4B, the image signaloutput from the second image sensor 12 varies from a state as shown inFIG. 5B to a state as shown in FIG. 5C. Thereafter, the document sheet Dis fed to a position as shown in FIG. 4D, the image signal output fromthe second image sensor 12 varies from the state as shown in FIG. 5Cback to the state as shown in FIG. 5B.

Accordingly, based on the change in the image signal output from thesecond image sensor 12 from the state as shown in FIG. 5B to the stateas shown in FIG. 5C, it is possible to detect a state where the leadingend of the document sheet reaches the aforementioned position to blockthe optical path. Additionally, based on the change in the image signaloutput from the second image sensor 12 from the state as shown in FIG.5C to the state as shown in FIG. 5B, it is possible to detect a statewhere the trailing end of the document sheet passes through theaforementioned position to block the optical path.

[Control System of MFP]

Subsequently, a control system of the MFP 1 will be described withreference to FIG. 6. The MFP 1 includes a controller 31, a reading unit32, a printing unit 33, a memory card reading/writing unit 34, a LANcommunication unit 35, a PSTN communication unit 36, an operation unit37, and a display unit 38.

The controller 31 includes known elements such as a CPU, a ROM, and aRAM. The CPU of the controller 31 takes control of each elementsincluded in the MFP 1 when running control programs stored on the ROM orthe RAM.

The reading unit 32 is configured to read an image on a document sheetand provided with the already-described first image sensor 11, secondimage sensor 12, and ADF 5. The ADF 5 includes a document feedingmechanism 5 a configured to feed document sheets along the feeding pathon a sheet-by-sheet basis, and a document detecting sensor 5 bconfigured to detect whether there is a document set on the ADF 5.

The printing unit 33 is configured with a printing mechanism employingan electrophotographic technique or an inkjet technique. In the copyfunction of the MFP 1, the printing unit 33 is used to print an imageread by the reading unit 32. Further, in the facsimile function of theMFP 1, the printing unit 33 is used to print an image received viafacsimile communication.

The memory card reading/writing unit 34 is configured to, when aremovable medium such as a memory card and a USB memory is attachedthereto, read data from the removable medium and/or write data onto theremovable medium.

The LAN communication unit 35 is configured with a communicationinterface device complying with a wireless LAN and a communicationinterface device complying with a wired LAN. Through the LANcommunication unit 35, the MFP 1 can perform data communication with adevice via a LAN.

The PSTN communication unit 36 is configured with various devices, suchas a facsimile modem and an audio CODEC, which are necessary forconnection with a public switched telephone networks (PSTN). Through thePSTN communication unit 36, the MFP 1 can communicate with a device(e.g., a facsimile machine) via the PSTN. For instance, when the useruses the facsimile function of the MFP 1, transmission/reception of datais carried out via the PSTN communication unit 36.

The operation unit 37 is an input device which the user operates whenproviding various commands to the MFP 1, and includes a touch panel,various buttons, and switches. The display unit 38 is an output deviceconfigured to notify the user about an operational status of the MFP 1,and includes a liquid crystal display (LCD) device.

[Image Reading Process]

Subsequently, an explanation will be provided about an image readingprocess that the MFP 1 performs, with reference to FIGS. 7, 8A, 8B, 9A,9B, 10A and 10B. A process shown in FIG. 7 is executed by the controller31 in response to some sort of event occurring in the MFP 1.

When the process shown in FIG. 7 is launched, the controller 31 firstlydetermines whether a reading start command has been issued (S110). Thedetermination as to whether the reading start command has been issuedcan be made, for instance, based on whether a scan button provided tothe operation unit 37 has been pressed. However, in this respect, such areading start command may be received from an external device (e.g., aPC) via the LAN communication unit 35. Thus, a method for determiningwhether the reading start command has been issued is not limited to aspecific one.

When determining that a reading start command has not been issued (S110:No), the controllers 31 performs one or more processes other than theimage reading process (S115). After that, the controller 31 terminatesthe process shown in FIG. 7. It is noted that since the one or moreprocesses other than the image reading process are not directly relatedto any major aspects of the present invention, a further explanationabout them will be omitted in the following description. Meanwhile, whendetermining that a reading start command has been issued (S110: Yes),the controllers 31 determines whether the document detecting sensor 5 bis ON (S120).

When determining that the document detecting sensor 5 b is OFF (S120:No), the controller 31 determines that there is no document sheet set onthe ADF 5, and performs an FB reading process (S125). Thereafter, thecontroller 31 terminates the process shown in FIG. 7. It is noted thatsince the FB reading process, which is for reading out an image from adocument sheet placed on the document table 3A, is not directly relatedto any major aspects of the present invention, a further explanationabout it will be omitted in the following description.

Meanwhile, when determining that the document detecting sensor 5 b is ON(S120: Yes), the controller 31 determines that there is a document sheetset on the ADF 5, and resets a counter value “n” to “1” (S130). The, thecontroller 31 performs a process to feed a first document sheet anddetect a leading end thereof (S135).

A detailed procedure of S135 is shown in FIG. 8A. When the process ofS135 is started, the controller 31 firstly begins document feeding at afeeding speed higher than a standard speed (S205). The standard speed isa feeding speed applied when the MFP 1 reads a color image from adocument sheet with the first image sensor 11 or the second image sensor12 and acquires image data of the read color image.

The standard speed varies depending on a reading resolution. Namely, alower standard speed is employed for a higher reading resolution. InS205, the controller 31 starts document feeding at a feeding speedhigher than such a standard speed. Thereby, it is possible to convey thedocument sheet to the reading start position more quickly than a casewhere document feeding is started at the standard speed. It is notedthat a detailed explanation will be provided later about a differencebetween the “standard speed” and the “feeding speed higher than thestandard speed”.

Next, the controller 31 controls operations of the first image sensor 11and the second image sensor 12 in a first control pattern and checks achange in the image signal output from the second image sensor 12(S210). When controlled in the first control pattern, the first imagesensor 11 and the second image sensor 12 work in respective operationalstates as shown in FIG. 11A.

Specifically, the controller 31 controls the light emitting portion 11 aof the first image sensor 11 to emit green-colored light and turns OFFthe light emitting portion 12 a of the second image sensor 12. In thisstate, the controller 31 controls the light receiving portion 12 b ofthe second image sensor 12 to receive light. Thereby, the second imagesensor 12 outputs an image signal.

Further, the controller 31 feeds the document sheet at such a speed asto feed the document sheet in the sub scanning direction by one lineevery single light receiving operation. Namely, the “feeding speedhigher than the standard speed” referred to in S205 denotes “such aspeed as to feed a document sheet by one line in the sub scanningdirection every single light receiving operation.”

As will be described in detail later, in the embodiment, the “standardspeed” referred to in S205 denotes “such a speed as to feed a documentsheet by one line in the sub scanning direction every four lightreceiving operations. Thereby, it is possible to understand that the“feeding speed higher than the standard speed” referred to in S205 isadequately higher than the “standard speed.”

Further, “such a speed as to feed a document sheet by one line in thesub scanning direction” is lower as the reading resolution, which isarbitrarily settable by the user, is higher. However, in S210, as far asit is possible to detect the leading end of the document sheet withoutproblems, an excessively high reading resolution is not necessary fordetecting the leading end of the document sheet. Therefore, in S210, thereading resolution may be changed to be lower than a user-setresolution. When the reading resolution is changed to be lower than auser-set resolution, the aforementioned “feeding speed higher than thestandard speed” becomes further higher than the “standard speed.”

When a leading end of a first document sheet does not reach (thedetection position on) the optical path extending from the light guide27 to the light receiving portion 12 b, the image signal output from thesecond image sensor 12 has a waveform as shown in FIG. 5B. Meanwhile,when the leading end of the first document sheet reaches (the detectionposition on) the optical path extending from the light guide 27 to thelight receiving portion 12 b, the image signal output from the secondimage sensor 12 has a waveform as shown in FIG. 5C. Therefore, in S210,the controller 31 checks whether there is a change between the aboveimage signals (S210).

Based on a check result as to whether there is a change in the imagesignal output from the second image sensor 12, the controller 31determines whether the controller 31 has detected the leading end of thefirst document sheet (S215). When determining that the controller 31 hasnot yet detected the leading end of the first document sheet (S215: No),the controller 31 goes back to S210, and repeatedly executes the stepsS210 to S215. Thus, the controller 31 continues to execute S210 everyone-line document feeding (each time the controller 31 feeds the firstdocument sheet by one line), until the controller 31 detects the leadingend of the first document sheet.

Meanwhile, when determining that the controller 31 has detected theleading end of the first document sheet (S215: Yes), the controller 31determines whether a second-side reading start point of the firstdocument sheet has reached the reading position for the second imagesensor 12 (S225).

Specifically, the second-side reading start point is arbitrarilysettable, and for instance, the leading end of the document sheet may beset as the second-side reading start point. Alternatively, a positionthat is shifted from the leading end to the trailing end by apredetermined amount of margin may be set as the second-side readingstart point.

In S225, the controller 31 determines whether the second-side readingstart point of the first document sheet has reached the reading positionfor the second image sensor 12, with a reference time as a time when thecontroller 31 detects the leading end of the first document sheetpassing through the detection position.

A distance of a section on the feeding path between the detectionposition to detect the leading end of the document sheet passingtherethrough and the reading position for the second image sensor 12 isa known value. In addition, a feeding speed at which the document sheetis conveyed within the above section is a known value. Further, in anyof a case where the leading end of the document sheet is set as thesecond-side reading start point and a case where the position shiftedfrom the leading end to the trailing end by the predetermined amount ofmargin is set as the second-side reading start point, a distance betweenthe leading end of the document sheet and the second-side reading startpoint is a known value.

Accordingly, by using the known values, it is possible to calculate aperiod of time between a time to detect the leading end of the documentsheet passing through the detection position and a time when thesecond-side reading start point of the document sheet, being conveyed ata predetermined feeding speed, reaches the reading position for thesecond image sensor 12. Therefore, in S225, it is possible to determinewhether the second-side reading start point of the first document sheethas reached the reading position for the second image sensor 12, basedon whether the above calculated period of time has elapsed afterdetection of the leading end of the document sheet passing through thedetection position.

Moreover, when a distance by which the document sheet is fed in responseto the controller 31 providing a unit of driving signals to the documentfeeding mechanism 5 a is a known value, it is possible to calculate howmany units of driving signals the controller 31 needs to provide afterdetection of the leading end of the document sheet passing through thedetection position so as to make the second-side reading start positionreach the reading position for the second image sensor 12.

Thus, in this case, in S225, it is possible to determine whether thesecond-side reading start point of the first document sheet has reachedthe reading position for the second image sensor 12, based on whetherthe controller 31 provides a predetermined number of units of drivingsignals to the document feeding mechanism 5 a after detection of theleading end of the document sheet passing through the detectionposition.

Based on the aforementioned determinations, when determining that thesecond-side reading start point of the first document sheet has notreached the reading position for the second image sensor 12 (S225: No),the controller 31 goes back to S225. Thereby, the controller 31continues to feed the document sheet at a feeding speed higher than thestandard speed until the second-side reading start point of the documentsheet reaches the reading position for the second image sensor 12. Then,when determining that the second-side reading start point of the firstdocument sheet has reached the reading position for the second imagesensor 12 (S225: Yes), the controller 31 changes the document feedingspeed to the standard speed (S230).

After completing execution of S230 (which corresponds to completingexecution of S135 in FIG. 7), subsequently, the controller 31 performsan n-th document second-side image data acquiring process to acquireimage data of a second side of an n-th document sheet (S140). It isnoted that in first execution of S140, the counter value “n” is still“1” as set in S130. In this case, the controller 31 performs a firstdocument second-side image data acquiring process to acquire image dataof the second side of the first document sheet in S140.

FIG. 8B shows a specific procedure of the n-th document second-sideimage data acquiring process that is executed in S140 to acquire imagedata of the second side of an n-th document sheet. After launching then-th document second-side image data acquiring process, firstly, thecontroller 31 controls the operations of the first and second imagesensors 11 and 12 in a second control pattern, and acquires image dataof the second side of the n-th document sheet from the second imagesensor 12 (S320).

When controlled in the second control pattern, the first image sensor 11and the second image sensor 12 work in respective operational states asshown in FIG. 11B. Specifically, at a first stage, the controller 31controls the light emitting portion 11 a of the first image sensor 11 toemit blue-colored light and turns ON the light emitting portion 12 a ofthe second image sensor 12 to emit red-colored light. In this state, thecontroller 31 controls the light receiving portion 11 b of the firstimage sensor 11 and the light receiving portion 12 b of the second imagesensor 12 to receive light. Thereby, each of the first and second imagesensors 11 and 12 outputs an image signal.

Further, at a second stage, the controller 31 turns OFF the lightemitting portion 11 a of the first image sensor 11 and controls thelight emitting portion 12 a of the second image sensor 12 to emitgreen-colored light. In this state, the controller 31 controls the lightreceiving portion 11 b of the first image sensor 11 and the lightreceiving portion 12 b of the second image sensor 12 to receive light.Thereby, each of the first and second image sensors 11 and 12 outputs animage signal.

In the same manner, at a third stage and a fourth stage, the controller31 takes ON/OFF control for the first and second image sensors 11 and 12as shown in FIG. 11B, such that each of the first and second imagesensors 11 and 12 outputs an image signal.

Then, the controller 31 performs document feeding at such a feedingspeed as to feed the document sheet by one line in the sub scanningdirection every four light receiving operations (i.e., every executionof the aforementioned four stages of light receiving operations). In theembodiment, such a feeding speed is the “standard speed” referred to inS205.

Each image signal output from the second image sensor 12 at theaforementioned first to third stages is a signal corresponding to animage read out of the second side of the n-th document sheet. Therefore,the controller 31 acquires the image signals output at the first tothird stages and stores the acquired image signals as image data into anoutput buffer. The image signals output at the fourth stage are not usedin S320.

The image data stored in the output buffer is finally transferred to adifferent output destination, and for instance, printed by the printingunit 33 or saved by the memory card reading/writing unit 34. It is notedthat various kinds of data processing in the different outputdestination are not directly related to any major aspects of the presentinvention, a further explanation about them will be omitted in thefollowing description.

After execution of S320, the controller 31 determines whether afirst-side reading start point of the n-th document sheet has reachedthe reading position for the first image sensor 11 (S325). Thedetermination in S325 may be made in the same manner as thedetermination in S225.

A distance of a section on the feeding path between the detectionposition to detect the leading end of the document sheet passingtherethrough and the reading position for the first image sensor 11 islonger than the distance between the detection position and the readingposition. Accordingly, the determination in each of S225 and S325 ismade in consideration of the difference between the two distances.

When determining that the first-side reading start point of the n-thdocument sheet has not reached the reading position for the first imagesensor 11 (S325: No), the controller 31 goes back to S325. Thereby, thecontroller 31 continues to execute S320 every one-line document feeding(each time the controller 31 feeds the n-th document sheet by one line)until the first-side reading start point of the n-th document sheetreaches the reading position for the first image sensor 11.

Then, when determining that the first-side reading start point of then-th document sheet has reached the reading position for the first imagesensor 11 (S325: Yes), the controller 31 completes execution of S140 andthen performs a process to acquire image data of both sides of the n-thdocument sheet and detect a trailing end of the n-th document sheet(S145).

FIG. 9A shows a specific procedure of the process to be executed inS145. After launching the process, initially, the controller 31 controlsthe operations of the first and second image sensors 11 and 12 in thesecond control pattern, to acquire image data of the first side of thedocument sheet from the first image sensor 11, acquire image data of thesecond side of the document sheet from the second image sensor 12, andcheck a change in the image signal output from the second image sensor12 (S410).

As described above, when controlled in the second control pattern, thefirst image sensor 11 and the second image sensor 12 work in theirrespective operational states as shown in FIG. 11B. At this time, eachimage signal output from the first image sensor 11 at the first, third,and fourth stages is a signal corresponding to an image read out of thefirst side of the n-th document sheet. Therefore, the controller 31acquires the image signals output at the first, third, and fourth stagesand stores the acquired image signals as image data into the outputbuffer.

Meanwhile, each image signal output from the second image sensor 12 atthe first to third stages is a signal corresponding to the image readout of the second side of the n-th document sheet. Accordingly, thecontroller 31 acquires the image signals output at the first to thirdstages and stores the acquired image signals as image data into theoutput buffer.

In addition to the process to acquire the image data of each side of then-th document sheet, in S410, the controller 31 checks a change in theimage signal output from the second image sensor 12 at the fourth stage.The image signal output from the second image sensor 12 at the fourthstage has a waveform as shown in FIG. 5C, when the trailing end of then-th document sheet exists on the optical path extending from the lightguide 27 to the light receiving portion 12 b. Meanwhile, the imagesignal output from the second image sensor 12 has a waveform as shown inFIG. 5B, when the trailing end of the n-th document sheet has passedthrough (the detection position on) the optical path extending from thelight guide 27 to the light receiving portion 12 b. Thus, in S410, thecontroller 31 checks whether there is a change between the above imagesignals.

The controller 31 determines whether the controller 31 has detected thetrailing end of the n-th document sheet, based on the checked change inthe image signal (S415). When determining that the controller 31 has notyet detected the trailing end of the n-th document sheet (S415: No), thecontroller 31 goes back to S410 and repeatedly performs the steps S410and S415. Therefore, the controller 31 continues to execute S410 everyone-line document feeding, until the controller 31 detects the trailingend of the n-th document sheet.

Meanwhile, in S415, when determining that the controller 31 has detectedthe trailing end of the n-th document sheet (S415: Yes), the controller31 controls the operations of the first and second image sensors 11 and12 in the second control pattern, to acquire image data of the firstside of the document sheet from the first image sensor 11 and acquireimage data of the second side of the document sheet from the secondimage sensor 12 (S420).

Namely, among the operations executed in S410, the controller 31 stopsonly operations necessary for detecting the trailing end of the n-thdocument sheet, and continuously performs the other operations in S420as well, to acquire image data of the both sides of the n-th documentsheet.

After execution of S420, the controller 31 determines whether asecond-side reading end point of the n-th document sheet has reached thereading position for the second image sensor 12 (S425). Thedetermination in S425 may be made in a manner conforming to the methodfor the determination in S225 or S325.

For example, a distance on the feeding path between the detectionposition to detect the trailing end of the document sheet passingtherethrough and the reading position for the second image sensor 2 is aknown value. Hence, it is possible to calculate a period of time betweena time to detect the trailing end of the document sheet passing throughthe detection position and a time when the second-side reading end pointof the document sheet, being conveyed at a predetermined feeding speed,reaches the reading position for the second image sensor 12. Therefore,in S425, it is possible to determine whether the second-side reading endpoint of the n-th document sheet has reached the reading position forthe second image sensor 12, based on whether the above calculated periodof time has elapsed after detection of the trailing end of the documentsheet passing through the detection position.

When determining that the second-side reading end point of the n-thdocument sheet has not reached the reading position for the second imagesensor 12 (S425: No), the controller 31 goes back to S420 and repeatedlyperforms the steps S420 and S425. Therefore, the controller 31 continuesto execute S420 every one-line document feeding, until the second-sidereading end position of the n-th document sheet reaches the readingposition for the second image sensor 12.

Meanwhile, when determining that the second-side reading end point ofthe n-th document sheet has reached the reading position for the secondimage sensor 12 (S425: Yes), the controller 31 completes execution ofS145 in FIG. 7 and then determines whether the document detecting sensor5 b is ON (S150).

When the document detecting sensor 5 b is ON (S150: Yes), it means thatthere is a document sheet left on the ADF 5. When the document detectingsensor 5 b is OFF (S150: No), it means that all document sheets set onthe ADF 5 have completely been fed, and there is no document sheet lefton the ADF 5.

When there is a document sheet left on the ADF 5 (S150: Yes), thecontroller 31 increments the counter value “n” by one (S155). Them, thecontroller 31 performs a process to feed a new n-th document sheet,detect a leading end of the n-th document sheet, and acquire image dataof the first side of the (n−1)-th document sheet (S160).

FIG. 9B shows a specific procedure of the process to be executed inS160. When launching the process, initially, the controller 31 controlsthe operations of the first and second image sensors 11 and 12 in thesecond control pattern, to acquire image data of the first side of thedocument sheet from the first image sensor 11 and check a change in theimage signal output from the second image sensor 12 (S510).

In S510, the controller 31 acquires image signals output from the firstimage sensor 11 at the first, third, and fourth stages, and stores theacquired image signals as image data into the output buffer.

Further, in S510, the controller 31 checks a change in the image signaloutput from the second image sensor 12 when coming into the fourthstage, in the same manner as S410. In this respect, however, unlikeS410, the image signal output from the second image sensor 12 at thefourth stage in S510 changes in the same fashion as S210.

Namely, when the leading end of the n-th document sheet has not reach(the detection position on) the optical path extending from the lightguide 27 to the light receiving portion 12 b, the image signal outputfrom the second image sensor 12 has a waveform as shown in FIG. 5B.Meanwhile, when the leading end of the n-th document sheet has reached(the detection position on) the optical path extending from the lightguide 27 to the light receiving portion 12 b, the image signal outputfrom the second image sensor 12 has a waveform as shown in FIG. 5C.Thus, in S510, the controller 31 checks whether there is a changebetween the above image signals.

The controller 31 determines whether the controller 31 has detected theleading end of an n-th document sheet, based on the checked change inthe image signal (S515). When determining that the controller 31 has notdetected the leading end of an n-th document sheet (S515: No), thecontroller 31 goes back to S510 and repeatedly performs the steps S510and S515. Thus, the controller 31 continues to execute S510 everyone-line document feeding, until the controller 31 detects the leadingend of the n-th document sheet.

Meanwhile, when determining that the controller 31 has detected theleading end of an n-th document sheet (S515: Yes), the controller 31controls the operations of the first and second image sensors 11 and 12in the second control pattern, to acquire image data of the first sideof the document sheet (i.e., the (n−1)-th document sheet) from the firstimage sensor 11 (S520).

Namely, among the operations executed in S510, the controller 31 stopsonly operations necessary for detecting the leading end of the n-thdocument sheet, and continuously performs the other operations in S520as well, to acquire image data of the first side of the n-th documentsheet.

After execution of S520, the controller 31 determines whether thesecond-side reading start point of the n-th document sheet has reachedthe reading position for the second image sensor 12 (S525). Thedetermination in S525 may be made in the same manner as thedetermination in S225.

When determining that the second-side reading start point of the n-thdocument sheet has not reached the reading position for the second imagesensor 12 (S525: No), the controller 31 goes back to S520 and repeatedlyperforms the steps S520 and S525. Thus, the controller 31 continues toperform S520 every one-line document feeding, until the second-sidereading start point of the n-th document sheet reaches the readingposition for the second image sensor 12.

Then, when determining that the second-side reading start point of then-th document sheet has reached the reading position for the secondimage sensor 12 (S525: Yes), the controller 31 completes execution ofS160 in FIG. 7 and then performs a process to acquire image data of thesecond side of the n-th document sheet and acquire image data of thefirst side of the (n−1)-th document sheet (S165).

FIG. 10A shows a specific procedure of the process to be executed inS165. After launching the process, initially, the controller 31 controlsthe operations of the first and second image sensors 11 and 12 in thesecond control pattern, to acquire image data of the first side of thedocument sheet from the first image sensor 11 and acquire image data ofthe second side of the document sheet from the second image sensor 12.In S620, the controller 31 performs the same operations as S420.

After execution of S620, the controller 31 determines whether thefirst-side reading end point of the (n−1)-th document sheet has reachedthe reading position for the first image sensor 11 (S625). Thedetermination in S625 may be made in a manner conforming to the methodfor the determination in S425.

Namely, for instance, it is possible to calculate a period of timebetween a time to detect the trailing end of the document sheet passingthrough the detection position and a time when the first-side readingend point of the document sheet, being conveyed at a predeterminedfeeding speed, reaches the reading position for the first image sensor11. Accordingly, in S625, it is possible to determine whether thefirst-side reading end point of the (n−1)-th document sheet has reachedthe reading position for the first image sensor 11, based on whether theabove calculated period of time has elapsed after detection of thetrailing end of the document sheet passing through the detectionposition.

When determining that the first-side reading end point of the (n−1)-thdocument sheet has not reached the reading position for the first imagesensor 11 (S625: No), the controller 31 goes back to S620 and repeatedlyperforms the steps S620 and S625. Thus, the controller 31 continues toexecute 5620 every one-line document feeding, until the first-sidereading end point of the (n−1)-th document sheet reaches the readingposition for the first image sensor 11.

Then, when determining that the first-side reading end point of the(n−1)-th document sheet has reached the reading position for the firstimage sensor 11 (S625: Yes), the controller 31 completes execution ofS165 in FIG. 7 and then goes back to S140. Thus, as long as thecontroller 31 determines that the document detecting sensor 5 b is ON(S150: Yes), the controller 31 repeatedly executes the steps S140 toS165.

Specifically, when the controller 31 determines in S150 that thedocument detecting sensor 5 b is ON (S150: Yes), it means that there areone or more document sheets left on the ADF 5. The document sheets lefton the ADF 5 are processed on a sheet-by-sheet basis by repeatedexecution of the steps S140 to S165.

When the ADF 5 is brought into a state where there is no document sheetleft thereon through repeated execution of the steps S140 to S165 orsingle-time execution of the steps S135 to S145, the document detectingsensor 5 b is set OFF (S150: No).

In this case, the controller 31 performs a process to acquire image dataof the first side of the n-th document sheet (S170). FIG. 10B shows aspecific procedure of the process to be executed in S170. Afterlaunching the process, the controller 31 firstly controls the operationsof the first and second image sensors 11 and 12 in the second controlpattern, to acquire image data of the first side of the document sheetfrom the first image sensor 11 (S720). In S720, the controller 31performs the same operations as S520.

After execution of S720, the controller 31 determines whether thefirst-side reading end point of the n-th document sheet has reached thereading position for the first image sensor 11 (S725). The determinationin S725 may be made in the same manner as the determination in S625.

When determining that the first-side reading end point of the n-thdocument sheet has not reached the reading position for the first imagesensor 11 (S725: No), the controller 31 goes back to S720 and repeatedlyexecutes the steps S720 and S725. Thus, the controller 31 continues toexecute S720 every one-line document feeding, until the first-sidereading end point of the n-th document sheet reaches the readingposition for the first image sensor 11.

Then, when the first-side reading end point of the n-th document sheethas reached the reading position for the first image sensor 11 (S725:Yes), it means that all document sheets have completely been read.Therefore, the controller 31 ejects the document sheet at a speed higherthan the standard speed (S730). Then, at a time when certainly ejectingthe document sheet, the controller 31 stops document feeding (S735).Thus, the controller 31 completes execution of S170, and completes aseries of processes described above.

[Effects]

As described above, according to the MFP 1 of the embodiment, thecontroller 31 performs the steps S210, S410, and S510 to take control todetect the leading end and the trailing end of the document sheetpassing through the detection position, using the first image sensor 11and the second image sensor 12 that are provided to read images on thefirst and second sides of the document sheet.

Accordingly, the MFP 1 can be configured in a simplified manner withouta special sensor for detecting that the leading end or the trailing endof the document sheet being conveyed by the ADF 5 passes through apredetermined detection position.

Further, in the MFP 1, the detection position to detect the leading endand the trailing end of the document sheet is located upstream relativeto the second image sensor 12 on the feeding path. Therefore, it ispossible to detect the leading end or the trailing end of the documentsheet passing through the detection position before the leading end orthe trailing end of the document sheet reaches (the reading positionfor) the second image sensor 12.

Hence, it is possible to estimate in advance a moment when the leadingend or the trailing end of the document sheet reaches (the readingposition for) the second image sensor 12, based on the feeding speed anda relative positional relationship between the detection position andthe second image sensor 12. Further, it is possible to estimate inadvance a moment when the reading start point (located in apredetermined position relative to the leading end of the documentsheet) or the reading end point (located in a predetermined positionrelative to the trailing end of the document sheet) reaches (the readingposition for) the second image sensor 12.

Thus, since it is possible to estimate the above moments, for instance,it is possible to start acquisition of image data with the second imagesensor 12 based on a moment when the leading end or the reading startpoint of the document sheet reaches the second image sensor 12. Further,it is possible to stop the acquisition of image data with the secondimage sensor 12 based on a moment when the trailing end or the readingend point of the document sheet reaches the second image sensor 12.

Further, by executing S210, the controller 31 of the MFP 1 maintains thestate where the light emitting portion of the first image sensor 11emits light and the light emitting portion of the second image sensor 12does not emit light, until the leading end of the (first) document sheetpasses through the detection position.

Therefore, unlike a case to perform in parallel image reading with thesecond image sensor 12 and detection of the leading end or the trailingend of document sheet with the second image sensor 12, it is unnecessaryto set a moment to make the light emitting portion of the second imagesensor 12 emit light. Therefore, it is possible to more quickly detectthe leading end of the document sheet with the second image sensor 12.

Further, by executing S410 and S510, the controller 31 of the MFP 1 canperform in parallel image reading with the second image sensor 12 anddetection of the leading end or the trailing end of the document sheetwith the second image sensor 12. Accordingly, compared with aconfiguration to perform one of the image reading with the second imagesensor 12 and the detection of the leading end or the trailing end ofthe document sheet with the second image sensor 12 after competing theother, it is possible to more quickly perform the both (i.e., the imagereading with the second image sensor 12 and the detection of the leadingend or the trailing end of the document sheet with the second imagesensor 12).

Further, by executing S410 and S510, the controller 31 of the MFP 1 canperform in parallel image reading with the first image sensor 11 anddetection of the leading end or the trailing end of the document sheetwith the second image sensor 12. Accordingly, compared with aconfiguration to perform one of the image reading with the first imagesensor 11 and the detection of the leading end or the trailing end ofthe document sheet with the second image sensor 12 after competing theother, it is possible to more quickly perform the both (i.e., the imagereading with the first image sensor 11 and the detection of the leadingend or the trailing end of the document sheet with the second imagesensor 12).

Additionally, in the MFP 1, the light guide 27 constitutes a part of theoptical path. Therefore, compared with an optical path configuredwithout any member corresponding to the light guide 27, it is possibleto more easily form an optical path having a complicated shape.

Further, in the MFP 1, the light guide 27 is configured such that thelower end thereof faces the light emitting portion 11 a of the firstimage sensor 11 in a position outside a possible maximum width of thedocument sheet in the main scanning direction and that the upper endthereof faces the detection position in a position within a possibleminimum width of the document sheet in the main scanning direction.

Therefore, even when a document sheet with the maximum width is fed, itis possible to certainly make the light, which is emitted by the lightemitting portion 11 a, incident onto the lower end of the light guide27. Further, even when a document sheet with the minimum width is fed,it is possible to certainly make the document sheet, which is passingthrough the detection position, block the light emitted by the upper endof the light guide 27.

Further, in the MFP 1, the second pressing member 24 is formed with thereflection surface 24 that is disposed in a position away from thefeeding path. In such a configuration, the light emitted by the upperend of the light guide 27 passes through the detection position and thenreaches the reflection surface 24 of the second pressing member 24.Further, the light reflected from the reflection surface 24 a reachesthe light receiving portion 12 b of the second image sensor 12.

Therefore, when the reflection surface 24 a is set at a desired angle,it is possible to dispose the light receiving portion 12 b of the secondimage sensor 12 and the detection position in respective positions awayfrom each other. Thus, it is possible to adjust, in a favorable manner,a period of time between a time when the leading end of the documentsheet is detected in the detection position and a time when the readingstart point of the document sheet reaches the reading position for thesecond image sensor 12.

Hereinabove, the embodiment according to aspects of the presentinvention has been described. The present invention can be practiced byemploying conventional materials, methodology and equipment.Accordingly, the details of such materials, equipment and methodologyare not set forth herein in detail. In the previous descriptions,numerous specific details are set forth, such as specific materials,structures, chemicals, processes, etc., in order to provide a thoroughunderstanding of the present invention. However, it should be recognizedthat the present invention can be practiced without reapportioning tothe details specifically set forth. In other instances, well knownprocessing structures have not been described in detail, in order not tounnecessarily obscure the present invention.

Only an exemplary embodiment of the present invention and but a fewexamples of their versatility are shown and described in the presentdisclosure. It is to be understood that the present invention is capableof use in various other combinations and environments and is capable ofchanges or modifications within the scope of the inventive concept asexpressed herein. For example, the following modifications may befeasible.

In the aforementioned embodiment, the acquisition of the image data isstarted at the moment when the reading start point of the document sheetreaches the second image sensor 12 and ended at the moment when thereading end point of the document sheet reaches the second image sensor12.

However, the acquisition of the image data using the second image sensor12 may be started earlier than the moment when the leading end or thereading start point of the document sheet reaches the second imagesensor 12. Further, the acquisition of the image data using the secondimage sensor 12 may be ended later than the moment when the trailing endor the reading end point of the document sheet reaches the second imagesensor 12.

In those cases, when the MFP 1 is configured as described in theaforementioned embodiment, it is possible to specify a positioncorresponding to the leading end or the reading start point of thedocument sheet and a position corresponding to the trailing end or thereading end point of the document sheet. Accordingly, by cutting out aportion between the specified positions from the acquired image data, itis possible to acquire data equivalent to the image data acquired in theaforementioned embodiment.

In the aforementioned embodiment, the second image sensor 12 iscontrolled to emit green-colored light in S210. However, the secondimage sensor 12 may be controlled to emit red-colored light orblue-colored light in S210. Further, even in S210, the controller 31 maycontrol the operations of the first image sensor 11 and the second imagesensor 12 in the second control pattern. Further, in S210, thecontroller 31 may control, as needed, any two or three of three lightsources (which emit red-colored light, green-colored light, blue-coloredlight, respectively) of the second image sensor 12 to emit light.

The light guide 27 may be configured with a molded component oftransparent hard resin such as acrylic resin or a flexible componentsuch as an optical fiber. Further, the light guide 27 may include alight guide mechanism with one or more mirror surfaces to introducelight in an intended direction.

In the aforementioned embodiment, the second image sensor 12 is disposedin a fixed manner at an upstream side in the feeding direction for adocument sheet to be read, and the first image sensor 11 is disposed ina movable manner at a downstream side in the feeding direction. However,the first and second image sensors 11 and 12 may be disposed inrespective arbitrary positions. For example, even when the first andsecond image sensors 11 and 12 are disposed in the same fashion asdescribed in the aforementioned embodiment and the document sheet to beread is fed in a feeding direction opposite to that of theaforementioned embodiment, aspects of the present invention may beapplied. In this respect, however, it is needed to appropriately adjustthe position of the light guide 27 and a position where the documentsheet blocks the optical path.

In the aforementioned embodiment, the first image sensor 11 isconfigured to be movable such that the MFP 1 can be used as a flatbedscanner. However, the first image sensor 11 may be configured to beunmovable. In other words, the MFP 1 may be configured as a double-sidereading ADF scanner that cannot be used as a flatbed scanner.

In the aforementioned embodiment, exemplified as an image readeraccording to aspects of the present invention is the MFP 1 that hasmultiple functions as well as the image reading function. However,aspects of the present invention may be applied to an image scannerhaving only a single function, i.e., the image reading function.

What is claimed is:
 1. An image reader comprising: a first reading unitthat comprises: a first light emitting portion configured to emit lightonto a first side of a document sheet; and a first light receivingportion configured to receive the light reflected from the first side ofthe document sheet, so as to read out an image having a plurality ofpixels arranged along a main scanning direction from the first side ofthe document sheet; a second reading unit that comprises: a second lightemitting portion configured to emit light onto a second side opposite tothe first side of the document sheet; and a second light receivingportion configured to receive the light reflected from the second sideof the document sheet, so as to read out an image having a plurality ofpixels arranged along the main scanning direction from the second sideof the document sheet; a feeder configured to feed the document sheetalong a feeding path in a sub scanning direction perpendicular to themain scanning direction; a light guide unit configured to form anoptical path to guide light emitted by the first light emitting portionto the second light receiving portion, wherein the optical pathintersects the feeding path at a detection position such that thedocument sheet, which passes through the detection position on thefeeding path, blocks the light that is guided on the optical path fromthe first light emitting portion to the second light receiving portion,wherein the light guide unit comprises a transparent member configuredto transmit therethrough light incident onto a light receiving endthereof and emit the transmitted light from a light emitting endthereof, and wherein the transparent member is disposed such that thelight emitted from the light emitting end reaches the second lightreceiving portion via the detection position; and a controllerconfigured to determine that one of a leading end and a trailing end ofthe document sheet passes through the detection position, in response todetecting a change in a light receiving state of the second lightreceiving portion when the document sheet passes through the detectionposition in a first state where the first light emitting portion is setto an ON state to emit light and the second light emitting portion isset to an OFF state so as not to emit light.
 2. The image readeraccording to claim 1, wherein before starting image reading with one ofthe first reading unit and the second reading unit, the controllermaintains the first state where the first light emitting portion is setto an ON state to emit light and the second light emitting portion isset to an OFF state so as not to emit light until the controllerdetermines that the leading end of the document sheet passes through thedetection position.
 3. The image reader according to claim 1, whereinthe controller is further configured to set the second light emittingportion to the ON state or OFF state, wherein the controller isconfigured to control the second reading unit to perform image readingwhen the second light emitting portion is turned to the ON state, andwherein the controller is configured to, when the second light emittingportion is turned to the OFF state, set the first light emitting portionto the ON state, and determine that one of the leading end and thetrailing end of the document sheet passes through the detection positionin response to detecting the change in the light receiving state of thesecond light receiving portion.
 4. The image reader according to claim3, wherein the controller is configured to, when the second lightemitting portion is turned to the OFF state, set the first lightemitting portion to the ON state, and control the first reading unit toperform image reading.
 5. The image reader according to claim 1, whereinthe transparent member is disposed such that the light receiving endthereof faces the first light emitting portion outside a maximum widthof the document sheet in the main scanning direction and that the lightemitting end thereof faces the detection position within a minimum widthof the document sheet in the main scanning direction.
 6. The imagereader according to claim 1, further comprising a pressing memberdisposed in such a position as to face the second reading unit acrossthe feeding path, wherein the pressing member is configured to press thedocument sheet toward the second reading unit, wherein the pressingmember comprises a reflection surface formed in a position away from thefeeding path, and wherein the reflection surface is configured such thatthe light emitted from the light emitting end of the transparent memberreaches the reflection surface via the detection position and that thelight reflected from the reflection surface reaches the second lightreceiving portion.
 7. The image reader according to claim 1, wherein thedetection position is located upstream, in the sub scanning direction onthe feeding path, relative to a first reading position where the firstreading unit reads the first side of the document sheet and a secondreading position where the second reading unit reads the second side ofthe document sheet.
 8. An image reader comprising: a first reading unitthat comprises: a first light emitting portion configured to emit lightonto a first side of a document sheet; and a first light receivingportion configured to receive the light reflected from the first side ofthe document sheet, so as to read out an image having a plurality ofpixels arranged along a main scanning direction from the first side ofthe document sheet; a second reading unit that comprises: a second lightemitting portion configured to emit light onto a second side opposite tothe first side of the document sheet; and a second light receivingportion configured to receive the light reflected from the second sideof the document sheet, so as to read out an image having a plurality ofpixels arranged along the main scanning direction from the second sideof the document sheet; a feeder configured to feed the document sheetalong a feeding path in a sub scanning direction perpendicular to themain scanning direction; a light guide unit configured to form anoptical path to guide light emitted by the first light emitting portionto the second light receiving portion, wherein the optical path guidesthe light emitted by the first light emitting portion across the feedingpath at a detection position located upstream, in the sub scanningdirection on the feeding path, relative to a reading position where thesecond reading unit reads the second side of the document sheet, andagain across the feeding path at another position downstream, in the subscanning direction on the feeding path, relative to the detectionposition, to the second light receiving portion, wherein the light guideunit comprises a transparent member configured to transmit therethroughlight incident onto a light receiving end thereof and emit thetransmitted light from a light emitting end thereof, and wherein thetransparent member is disposed such that the light emitted from thelight emitting end reaches the second light receiving portion via thedetection position; and a controller configured to determine that one ofa leading end and a trailing end of the document sheet passes throughthe detection position, in response to detecting a change in a lightreceiving state of the second light receiving portion when the documentsheet passes through the detection position in a first state where thefirst light emitting portion is set to an ON state to emit light and thesecond light emitting portion is set to an OFF state so as not to emitlight.
 9. The image reader according to claim 8, wherein before startingimage reading with one of the first reading unit and the second readingunit, the controller maintains the first state where the first lightemitting portion is set to an ON state to emit light and the secondlight emitting portion is set to an OFF state so as not to emit lightuntil the controller determines that the leading end of the documentsheet passes through the detection position.
 10. The image readeraccording to claim 8, wherein the controller is further configured toset the second light emitting portion to the ON state or OFF state,wherein the controller is configured to control the second reading unitto perform image reading when the second light emitting portion isturned to the ON state, and wherein the controller is configured to,when the second light emitting portion is turned to the OFF state, setthe first light emitting portion to the ON state, and determine that oneof the leading end and the trailing end of the document sheet passesthrough the detection position in response to detecting the change inthe light receiving state of the second light receiving portion.
 11. Theimage reader according to claim 10, wherein the controller is configuredto, when the second light emitting portion is turned to the OFF state,set the first light emitting portion to the ON state, and control thefirst reading unit to perform image reading.
 12. The image readeraccording to claim 8, wherein the transparent member is disposed suchthat the light receiving end thereof faces the first light emittingportion outside a maximum width of the document sheet in the mainscanning direction and that the light emitting end thereof faces thedetection position within a minimum width of the document sheet in themain scanning direction.
 13. The image reader according to claim 8,further comprising a pressing member disposed in such a position as toface the second reading unit across the feeding path, wherein thepressing member is configured to press the document sheet toward thesecond reading unit, wherein the pressing member comprises a reflectionsurface formed in a position away from the feeding path, and wherein thereflection surface is configured such that the light emitted from thelight emitting end of the transparent member reaches the reflectionsurface via the detection position and that the light reflected from thereflection surface reaches the second light receiving portion.